One Illustrative Scenario for Internet E-Mail Delivery

Obligatory Introduction

Procmail is the Swiss Army Knife or Paragear
Plier of internet mail delivery: incredibly versatile,
but ill-suited to specific tasks and very dependent on the ingenuity
of the wielder.

Given that there are different learning styles, and one of
them is dissecting examples, I furnish this one as illustrative
of both procmail and internet mail delivery.

The example I've had up on the web has been oriented towards
people who were using or at least prepared to use procmail,
who knew what it was for and wanted to see a concrete example
which was a little more straightforward and accessible than the
usual references. But there are a lot of people out there who
don't have the sort of comprehensive experience which informs
them how procmail fits into the overall ecosystem
of internet mail delivery.

This is an attempt to illustrate more comprehensively how the
components work together.

The Scenario

You have a company, and you pay for an account at an ISP. You
also pay for a full-time internet connection. For any number of
reasons you don't have mail sent directly into your domain, instead
you funnel it through the ISP.

In this example your public presence e-mail is funneled through
a single account, ourco@a-big-isp.tld. Although your own e-mail
host is connected and mail could therefore be sent directly to
the accounts at ourco.tld, for any number of reasons you don't
advertise that fact.

This complexity is not introduced by the nature of internet
e-mail delivery; it is a consequence of tactical decisions, the
motives of which are not examined here.

In any case, once e-mail is sent to ourco@a-big-isp.tld you
want it distributed to the correct parties' separate e-mail accounts
within your domain.